Depending on their circumstances, it could also make sense that they would try hardest not to get pregnant at that time of the month.

Generally yes; I believe this is fairly well studied although I'm short on sources. IIRC, during ovulation, a woman would dress up with brighter colors (or dress nicer or something), have more flirtatious actions... I forgot if there were dietary changes. Also interesting (also IIRC), is that women prefer more masculine males during peak fertility (best genes), and prefer more feminine males during lowest fertility (best care).

Based upon empirical evidence, that would seem to be most true.

Though I'm sure it depends heavily on what else is going on in the person's life at that time.

Quite possibly, though presumably lap dancers are always trying to maximize their earnings, so any behavioral changes are likely to be subconscious.